Radiation Exposure and the Risk of Cancer
“Half of Children Receive Unnecessary CT Scans,” by Martin Beckford, Health Correspondent, May 20, 2011.
The number of children’s CT scans increases, yet are harmful and in many cases completely unnecessary since severe brain injuries are rare.
CT scans expose children to radiation, and are sometimes used for quicker evaluations and to appease worried parents. Doctors say that simple astute observance is equally safe. After all, that is what doctors do!
European guidelines denote that CT scans should be performed for children who have passed out for more than five minutes, show signs of amnesia, profuse vomiting, or suffered a serious head trauma. The researchers below checked out over 40,000 minor head trauma records and only 14 per cent were observed in emergency rooms versus CT scans.
A couple extra extra hours in the ward and observing children after the incident can prevent them from cancer-causing radiological damage during a crucial time in their development.
Half of children who suffer head injuries are unnecessarily being given scans that expose them to radiation, according to research.
Doctors say that simply observing the condition of young patients in emergency wards is equally safe, particularly as severe brain injuries are rare.
They claim that in many cases children are only given CT scans, which expose them to potentially dangerous doses of radiation, in order to ease their parents’ fears after they suffer an accident.
“CT isn’t bad if you really need, but you don’t want to use it in children who are at low risk for having a significant injury,” said Dr Lise Nigrovic of Children’s Hospital Boston, who led the study.
“For parents, this means spending a couple of extra hours in the emergency department in exchange for not getting a CT. It’s the children in the middle risk groups – those who don’t appear totally normal, but whose injury isn’t obviously severe – for whom observation can really help.”
Current guidelines from Nice, the health regulator in England and Wales, state that under-16s who arrive at A&E with a head injury should have a CT scan “requested immediately” if they have passed out for more than five minutes, suffered amnesia lasting the same amount of time, have vomited three or more times or appear to have suffered an intentional wound, road accident or fallen from a height.
However it concedes that “paediatric CT will result in increased lifetime risks of cancer compared to adult CT due to both the higher radiation doses currently delivered to children and their increased sensitivity to radiation-induced cancer over a longer life span”.
Because of the increased risk of cancer for children undergoing CT scans – a type of X-ray that sends several beams create a computer image of the inside of the head – researchers investigated how many of the procedures are necessary.
They looked at the records of 40,113 American children who had suffered minor blunt head trauma and identified 14 per cent who were observed in emergency wards rather than being scanned straight away.
The team, whose work is published in the June 2011 issue of Pediatrics, found that those who were observed were half as likely to have a CT scan later, particularly among those whose symptoms improved under observation.
Yet the incidence of traumatic brain injury, leading to surgery, hospital admission or death, was “equally uncommon” in those who had CT scans as those who were observed.
Researchers recommend keeping close watch over children with head injuries for between four and six hours, in order to reduce their exposure to radiation as their growing brain tissue is more sensitive than that of adults. In addition, young people have longer time in which to develop tumours.
Co-author Dr Nathan Kuppermann, chair of the Department of Emergency Medicine at UC Davis, said: “There is a clear need to develop appropriate and safe guidelines for decreasing the number of inappropriate head CT scans that we do on children.
“The results of this analysis demonstrate that a period of observation before deciding to use head CT scans on many injured children can spare children from inappropriate radiation when it is not called for, while not increasing the risk of missing important brain injuries.”
By Martin Beckford, Health Correspondent
“Radiation Risks and Pediatric Computed Tomography (CT): A Guide for Health Care Providers,”
December 22, 2008, by the National Cancer Institute at the National Institutes of Health.
The use of pediatric CT, a valuable imaging tool, has been increasing rapidly. Because of current and growing use of CT and the potential for increased radiation exposure to children undergoing these scans, pediatric CT is a public health concern. This brochure discusses the value of CT and the importance of minimizing the radiation dose, especially in children. It will address the following issues:
- CT as a diagnostic tool
- Unique considerations for radiation exposure in children
- Radiation risks from CT in children: a public health issue
- Immediate strategies to minimize CT radiation exposure to children
CT as a Diagnostic Tool
CT is extremely valuable, and can be a life-saving tool for diagnosing illness and injury in children. For an individual child, the risks of CT are small and the individual risk-benefit balance favors the benefit when used appropriately. Approximately 4-7 million CT examinations are performed annually on children in the U.S. The use of CT in adults and children has increased about 8-fold since 1980, with annual growth estimated at about 10% per year. Much of this increase is due to its utility in common diseases as well as technical improvements. Despite the many benefits of CT, a disadvantage is the inevitable radiation exposure. Although CT scans comprise up to about 12% of diagnostic radiological procedures in large U.S. hospitals, it is estimated that CT scans contribute approximately 45% of the U.S. population’s collective radiation dose from all medical x-ray examinations. CT is the largest contributor to medical exposure to the U.S. population.
Unique Considerations for Radiation Exposure in Children
Radiation exposure is a concern in both adults and children. However, there are three unique considerations in children.
- Children are considerably more sensitive to radiation than adults, as demonstrated in epidemiologic studies of exposed populations.
- Children also have a longer life expectancy than adults, resulting in a larger window of opportunity for expressing radiation damage.
- Children receive a higher dose than necessary when adult CT settings are used for children.
As a result, the risk for developing a radiation-related cancer can be several times higher for a young child compared with an adult exposed to an identical CT scan.
There is no need for these larger doses to children, and CT settings can be reduced significantly while maintaining diagnostic image quality. Therefore, children should not be scanned using adult CT exposure parameters. Adjustments are frequently not made in the CT exposure parameters that determine the amount of radiation children receive from CT, resulting in a greater radiation dose than necessary.
Radiation Risks from CT in Children: A Public Health Issue
Major national and international organizations responsible for evaluating radiation risks agree there probably is no low-dose radiation “threshold” for inducing cancers, i.e., no amount of radiation should be considered absolutely safe. Recent data from the atomic bomb survivors and other irradiated populations demonstrate small, but significant, increases in cancer risk even at the low levels of radiation that are relevant to pediatric CT scans. Effective doses from a single pediatric CT scan can range from about < 1 to 30 mSv (see table below). Among children who have undergone CT scans, approximately one-third have had at least three scans. Multiple scans present a particular concern. For example, three scans would be expected to triple the cancer risk of a single scan. In addition, more than one scan (more than one “phase”) may be done during a single examination, further increasing the radiation dose. A single scan during pediatric CT should be sufficient in the vast majority of cases.
It is important to stress that the individual cancer risks associated with CT scans are small. The highest lifetime risks estimated in the literature are less than 1 in 1000, and most estimates are substantially lower than that. The public health issue is the increasingly large pediatric population being exposed to these small risks.
The benefits of properly performed CT examinations should always outweigh the risks for an individual child; unnecessary exposure is associated with unnecessary risk. Minimizing radiation exposure from pediatric CT, whenever possible, will reduce the projected number of CT-related cancer deaths.
|Exam type||Relevant organ||Range of absorbed organ doses (mGy)||Range of effective doses (mSv) #|
|Head unadjusted* (200 mAs)||Brain||23- 49||1.8 – 3.8|
|Head adjusted (100 mAs)||Brain||11 – 25||0.9 – 1.9|
|Abdomen unadjusted (200 mAs)||Stomach||21 – 43||11 – 24|
|Abdomen adjusted (50 mAs)||Stomach||5 – 11||3 – 6|
|Chest x-ray PA||Lung||0.04 – 0.08||0.01 – 0.03|
|Chest x-ray lateral||Lung||0.04 – 0.10||0.03 – 0.06|
# Effective dose using the 2008 ICRP tissue weighting factors. Effective dose is used in radiation protection to express detriment to the whole body when only a part of the body is exposed. It takes into account the type of radiation and the sensitivity of the exposed organs / tissues (tissue weighting factor).
* “Unadjusted” refers to using the same settings as for adults. “Adjusted” refers to settings adjusted for body weight.
** Dose estimates for two views for each breast combined.
Immediate Measures to Minimize CT Radiation Exposure in Children
Physicians, other pediatric health care providers, CT technologists, CT manufacturers and various medical and governmental organizations share the responsibility to minimize CT radiation doses to children. Several immediate steps can be taken to reduce the amount of radiation that children receive from CT examinations:
- Perform only necessary CT examinations. Communication between pediatric health care providers and radiologists can determine the need for CT and the technique to be used. There are standard indications for CT in children, and radiologists should review reasons prior to every pediatric scan and be available for consultation when indications are uncertain. When appropriate, consider other modalities such as ultrasound or magnetic resonance imaging, which do not use ionizing radiation.
- Adjust exposure parameters for pediatric CT based on:
- Child size: guidelines based on individual size / weight parameters should be used.
- Region scanned: the region of the body scanned should be limited to the smallest necessary area.
- Organ systems scanned: lower mA and/or kVp settings should be considered for skeletal, lung imaging, and some CT angiographic and follow up examinations.
- Scan resolution: the highest quality images (i.e., those that require the most radiation) are not always required to make diagnoses. In many cases, lower-resolution scans are diagnostic. Be familiar with the dose descriptors available on CT scanners.1 Minimize the CT examinations that use multiple scans obtained during different phases of contrast enhancement (multiphase examinations). These multiphase examinations are rarely necessary, especially in body (chest and abdomen) imaging, and result in a considerable increase in dose.
|Issues to discuss with parents:
It should be noted that there have been studies in which parents were given information regarding the risks and benefits of CT, and this did not result in reduced compliance, but did result in parents asking more informed questions of the care providers.
Long-Term Strategies to Minimize CT Radiation
In addition to the immediate measures to reduce CT radiation exposure in children, long-term strategies are also needed.
- Encourage development and adoption of pediatric CT protocols.
- Encourage the use of selective strategies for pediatric imaging, such as for the pre-surgical evaluation of appendicitis.
- Educate through journal publications and conferences within and outside radiology specialties to optimize exposure settings and assess the need for CT in an individual patient. Disseminate information through associations, organizations, or societies involved in health care of children, including the American Academy of Pediatrics and the American Academy of Family Physicians. Provide readily available information sources on the World Wide Web (e.g. www.imagegently.org)
- Conduct further research to determine the relationship between CT quality and dose, to customize CT scanning for individual children and to clarify the relationship between CT radiation and cancer risk.
While CT remains a crucial tool for pediatric diagnosis, it is important for the health care community to work together to minimize the radiation dose to children. Radiologists should continually think about reducing exposure as low as reasonably achievable (ALARA), by using exposure settings customized for children. All physicians who prescribe pediatric CT should continually assess its use on a case-by-case basis. Used prudently and optimally, CT is one of our most valuable imaging modalities for both children and adults.
Link to article:
“The Doctor Says Get a CT Scan. Should You?”
By, Matthew Shulman, November 28, 2007, US News.
A new report in tomorrow’s issue of the New England Journal of Medicine raises serious concerns about the use, and overuse, of CT scanning. While individual risks of developing cancer from a CT scan, which emits high doses of radiation, are relatively low, the researchers worry that their rapid growth as a highly accurate diagnostic tool is exposing too much of the population—and an increasing amount of vulnerable children—to radiation and might be setting the stage for higher incidence of cancer in years to come. Around 62 million scans are performed per year, compared with only 3 million in 1980. Moreover, the researchers estimate that a third of those CT scans are entirely unnecessary—many of them now performed by cautious doctors on worried people with no symptoms at all.
How can you know if a CT scan is a wise move? U.S.News & World Report spoke with Fred Mettler, chief of radiology and nuclear medicine at New Mexico Veterans Health Care System and an expert on the effects of radiation, to find out.
How is a CT scan different from a traditional X-ray?
With a traditional X-ray—a chest X-ray, for example—radiation goes through you from one side to the other, with 3-D information ultimately projected onto a two-dimensional picture. With a CT scan, an X-ray tube rotates around the patient and presents the results to you as a three-dimensional picture. The advantage is that it’s much more sensitive, is high resolution, and offers much more anatomically specific information with great detail.
But a typical chest CT means around a 175-times-greater dose of radiation than a similar chest X-ray—that’s like 20 sets of mammograms. That range can be between 20 and 200 times higher depending on which part of the body is being scanned.
When is a CT scan definitely warranted?
If you think something is desperately wrong with you and you require an immediate answer. For example, an incredible abdominal pain or a severe acute headache as opposed to a migraine you have had off and on for years. If the CT scan is medically needed, don’t think about radiation. If you have excruciating head or abdominal pain, radiation exposure should not be high on the list of concerns.
But there’s no question that it’s overused—and I don’t think I can quarrel with the number of 30 percent.
How should judgment factor in?
One common problem for adults is renal stones. They have them all the time on and off, typically with horrible pain. It used to be that we gave them water and pain medication and told them to wait for the pain to pass. Now, all urologists want a CT scan done. I’ve seen people in their early 30s who have had 18 or 20 CT scans. They come in once a month, but there’s no evidence in the literature that this sort of thing is justified.
Another good example is if you have significant abdominal pain and go to the emergency room. The physician in the ER is buried with a “bazillion” patients. He can poke on your abdomen and see where the pain is emanating from, thinking it’s appendicitis. Then he’ll get some blood tests and if you have a high count will call a surgeon. Before the use of CT, around 20 percent of the time you got operated on and had a normal appendix.
Nowadays, doctors will immediately get a CT scan, and because it’s so sensitive and accurate for diagnosing appendicitis, less than 1 or 2 percent end up taking out normal appendixes. An additional advantage is that CT allows the doctor to see the entire abdomen and pelvis, the aorta, kidneys, and gallbladder. If your doctor wasn’t in fact right about the appendicitis, the CT scan will pick up a lot of other things that might be giving you your pain. It’s incredibly efficient and, of course, doctors can move you through ER much more quickly.
Is using a CT to determine appendicitis generally justified? Well, if the patient has severe pain in the right lower quadrant, then probably yes. On the other hand, is it justified for a little kid who is crying and doesn’t know what’s going on? In that case, probably not.
What are the risks involved in CT scanning?
Certainly a CT scan won’t make your hair fall out or anything so drastic. But the risk of cancer is there, and it depends on a few things. There’s the dose of the radiation, which depends substantially on the age of the patient. We know that kids are more sensitive and their risk of getting cancer is higher [when they are given] an adult dose. But these cancers tend not to occur for years or decades at least. For children, the risk of developing a fatal cancer is somewhere around 1 in 500 or 1 in 1,000—the older you get, the lower the risk becomes. So if someone is 90, for instance, there is virtually no cancer risk. For an adult, the risk is around 1 in 2,000.
At this point, people believe there is [a] linear relationship between the dose and the risk of cancer. So if you cut the dose in half, you also cut the risk in half. The question should be, can you optimize the dose by using a lower amount of radiation or can the scan be done only once instead of three times? For kids especially, doctors should really optimize with the lowest dose possible if a CT scan is warranted.
Is that happening?
I would say that five or so years ago, there’s no question they were actually getting adult doses. But after Dave Brenner [of Columbia] started hopping up and down about this problem and it was picked up in the media, pediatricians got very sensitive and manufacturers began putting pediatric dose settings on the CT machines. But, I don’t think the sensitivity is there for teenagers or young adults.
What are some alternatives to CT scanning that patients should know about or ask their doctors?
I would ask if there are ways we can find out the answer without using radiation. Using ultrasound, for example, or doing an MRI scan. Those don’t use ionizing radiation, so there is virtually no risk. And if the scan is definitely going to be done, ask about the dose you will be getting. If a child is getting a scan, a concerned parent should make sure the radiology technician is using the correct pediatric doses.
How do you prevent redundant CT scans and help patients to keep track of the scans they‘ve already had?
When our patients go to another hospital or doctor, we give them a CD of all their exams on it, and anyone can open them up, throw it on a PC, and have a look at the pics. That’s very helpful.
Are CT scans useful for asymptomatic patients?
I don’t recommend CT scans for asymptomatic patients. Take lung cancer screening for example. One article in the New England Journal of Medicine from last year concluded that CT scanning could prevent 80 percent of lung cancer deaths by catching lung nodules. Then in a 2007 Journal of the American Medical Association study, there was found to be no reduction in mortality by using CT scans for lung cancer. We shouldn’t do something with risk until studies determine what the risks and benefits actually are. A lot of scans are not justified, like the business of whole-body CT screening. No one has ever shown that these have more benefit than risk.
Link to article:
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